A defibrillator is a device that stores energy, typically in one or more high-voltage capacitors, and delivers the stored energy to a patient. In particular, a defibrillator delivers energy to a heart that is undergoing ventricular fibrillation and has lost its ability to contract. Ventricular fibrillation is particularly life threatening because activity within the ventricles of the heart is so uncoordinated that virtually no pumping of blood takes place. If untreated, the patient whose heart is undergoing fibrillation may die within a matter of minutes.
An electrical pulse delivered to a fibrillating heart may depolarize the heart and cause it to reestablish a normal sinus rhythm. An external defibrillator applies a defibrillation pulse via electrodes placed upon the chest of the patient. When a switch is closed, the defibrillator delivers at least some of the stored energy to the patient. In some cases, the patient may need multiple shocks, and different quantities of energy may be delivered with each shock.
The defibrillator may also monitor the patient via the electrodes, and generate a record of the condition and treatment of the patient. For example, the defibrillator may record an electrocardiogram (ECG) of the patient sensed via the electrodes. The defibrillator may keep track of the therapy provided to the patient by recording the types and energy levels of defibrillation pulses delivered to the patient and the time at which these pulses were delivered. The defibrillator may also include a microphone to make an audio recording of the treatment of the patient. These and other types of information surrounding the treatment of the patient, i.e., medical event information, may be stored within a memory of the defibrillator.
In some cases, the patient may be treated with more than one medical device. For example, the patient may have initially received prompt defibrillation therapy with an automatic external defibrillator (AED). In order to provide therapy as quickly as possible, many public and non-public venues, as well as first responders, such as police and fire personnel, are equipped with AEDs. An AED is designed to allow minimally trained operators to use the AED to deliver prompt therapy. AEDs differ from manual defibrillators in that AEDs can automatically analyze the ECG of the patient to determine whether defibrillation is necessary, and can automatically select energy levels for defibrillation pulses from preprogrammed progressions of energy levels. In most AED designs, the first responder is prompted to press a button when the AED determines that defibrillation is warranted and is ready to deliver a defibrillation pulse.
Typically, Advanced Cardiac Life Support (ACLS) trained emergency medical personnel, e.g. paramedics, arrive shortly thereafter to take over the treatment of the patient with a second defibrillator, which is usually more fully featured than an AED. The paramedics may need to use the second defibrillator to treat the patient. When the patient arrives at the emergency department of a hospital, the patient may be treated with a third defibrillator located therein. Each defibrillator used to treat the patient will store medical event information concerning the treatment.